I like to grill the flank steak, but you can use a grill pan on the stove, too.
Flank Steak Sandwiches
1 pound flank steak
salt and pepper to taste
1/2 cup mayonnaise
1/2 cup Greek yogurt
1 clove garlic, grated on microplane or very finely chopped
juice of one lemon
1/4 cup finely minced fresh herbs (rosemary, sage, chives, or others)
crusty bakery rolls
arugula
Heat outdoor grill or grill pan to high heat.
Meanwhile, make the sauce by combining mayo, yogurt, garlic, lemon juice, and herbs.
Season steak generously with salt and pepper. Grill steak about 5 minutes on first side. Flip it and grill 3-5 minutes on the other side. Cook to medium rare or medium. Let the steak rest for 5 minutes for slicing. Grill the rolls for a few seconds to toast them.
To slice flank steak, cut against the grain, to make 1/2 inch slices (or thinner if you can). Spread the sauce onto the bread, top with steak and arugula. Serve with extra sauce.